Modification of pomegranate waste with iron ions a green composite for removal of Pb from aqueous solution: equilibrium, thermodynamic and kinetic studies

Pomegranate waste modified with Fe(2+) and Fe(3+) ions followed with carbonization were used as an adsorbent to remove the Pb(2+) ions from aqueous solution. To optimum the highest adsorption efficiency, adsorption experiments were conducted on iron modified carbons by batch technique. The characteristic of composite was studied by scanning electron microscope (SEM) and Fourier transform infrared spectrometer (FT-IR). The best pH for control of chemical adsorption was selected within pH of 6.0–6.5. It was observed that the contact time of 90 min, initial concentration 50.0 ppm, and adsorbent dose, 1.0 g/100 ml solution was found to be optimum conditions. On this condition, the maximum adsorption capacity was obtained 27.5 and 22.5 mg/g for Fe(2+) and Fe(3+) impregnated pomegranate peel carbons (PPC), respectively. The value of C(id), 1.584 for Fe(2+)-PPC and 0.552 for Fe(3+)-PPC, indicates that the effect of the boundary layer is more important in adsorption of Pb(2+) by Fe(2+)-PPC and the pore diffusion is the rate limiting mechanism after 30 min. Thermodynamic parameters of Gibbs free energy, enthalpy, and entropy of Pb(2+) adsorption on iron-modified carbons suggest that the adsorption process is favorable and spontaneous under the optimum condition.